This invention relates broadly to a portable bleacher construction and, more particularly, pertains to a jack system for leveling and stabilizing a portable bleacher in a stationary position upon a ground surface.
There are various instances where events, particularly outdoor events, are to be staged which require the availability of seating for a viewing audience. Permanent seating, such as bleachers, can be constructed for events which are always held in the same place. For one-time events or less frequent events, temporary seating such as portable bleachers can be employed. Portable bleachers can also be used to supplement existing permanent seating to increase seating capacity, if desired, for certain events. One of the characteristics of such portable seating is that the mobile framework carrying the seating must be stabilized and leveled on ground surfaces which are frequently uneven and vary from site to site.
Portable bleacher constructions are known in which one section of seating is permanently fixed to a wheeled framework and at least one other section of seating is pivotally mounted thereto. Hydraulic cylinders or other mechanical devices are often used to pivot the movable section between a nested, travel position and an operative, seating position. In order to stabilize and level the bleacher construction prior to use, it has been the practice to install a plurality (i.e. 10-14) of individually operated jacks along the framework. Typically, the jacks are installed such that a series of jacks are located on each side of the framework. In operation, the operator must swivel each jack down from a storage mode, and then each jack must be manually cranked from a squatting or kneeling position to adjust for the particular terrain, to stabilize and level the portable bleacher. This necessitates that an operator will expend a great deal of time and energy adjusting the jacks on each side of the framework.
Accordingly, it would be desirable to markedly reduce the labor-intensive efforts required in deploying and individually adjusting the jacks employed in a portable seating arrangement. It would also be desirable to shorten the time needed to efficiently effect leveling of the mobile framework supporting the portable seating.
It is one object of the present invention to provide a portable bleacher construction equipped with a stabilizing jack system in which an operator can control the deployment and operation of the jacks to stabilize and level the portable bleacher construction with a minimum of time and effort.
It is also an object of the present invention to provide a portable bleacher framework with at least one pair of leveling jacks on opposite sides of the framework such that a control arrangement on one side of the framework is employed to independently adjust the positioning of both jacks.
It is a further object of the present invention to provide a stabilizing jack system for a portable bleacher in which a plurality of jacks disposed on each side of the portable bleacher framework may be operated in a standing position from one side of the framework.
In one aspect of the invention, a portable bleacher construction includes a wheeled framework for supporting a plurality of bleacher seats thereon in a mobile travel condition and a stationary seating condition. At least one pair of leveling jacks is located on opposite sides of the framework for stabilizing the framework in the seating position upon a ground surface. The invention contemplates a small number of high-capacity jacks in selected locations on the framework, to provide ease of operation and to increase stability to the portable bleacher construction. In a preferred form, four jacks are mounted to the framework to provide a stable stance, and each jack has a high sway load capacity to provide a high degree of lateral stability. In a particularly preferred form, a control arrangement is located on one side of the framework for separately controlling the deployment and leveling of both jacks in each pair of jacks. The framework includes a pair of parallel, spaced longitudinal beams interconnected by a pair of transverse end beams. A pair of wheel assemblies are located one on each of the longitudinal beams between the transverse end beams. Each jack is mounted to one of the longitudinal beams. Each jack has an upper tubular member affixed to one of the beams, and a lower tubular member with a ground engaging foot telescopically received and movably mounted in the upper tubular member for upward and downward movement relative thereto. The control arrangement is preferably interconnected with one of the jacks in each pair, and is located on a rear one of the longitudinal beams.
In one form, the control arrangement includes a first rotatable crank assembly and a second rotatable crank assembly movably mounted on an upper end of the upper tubular member of the jack disposed on the rear longitudinal beam. Each crank assembly is operably interconnected with one of the jacks, and the crank assemblies are operable to move the lower tubular members of the jacks on opposite sides of the framework upwardly and downwardly independent of each other. The first rotatable crank assembly has a first S-shaped handle pivotally mounted to a shortened transfer rod projecting into the upper end of the upper tubular member of the jack disposed on the rear longitudinal beam. The second rotatable crank assembly has a second S-shaped handle pivotally mounted to an elongated transfer rod extending from the jack on the rear longitudinal beam to the jack on the front longitudinal beam. The upper tubular member of the jack on the rear longitudinal beam includes clamp structure adapted for engagement with the first handle and the second handle for selectively retaining the first handle and the second handle in an inoperative position when not in use. The first handle and the second handle are disengaged from the clamp structure and pivoted upwardly on their respective transfer rods to an operative position, after which the handles are separately rotated to turn the transfer rods and operate the jacks, to effect movement of the lower tubular members against the ground surface. In a preferred form, at least one pair of jacks is located between the wheel assemblies and one of the transverse end beams, and another pair of jacks is located between the wheel assemblies and the other of the transverse end beams.
The invention also contemplates a portable bleacher construction having a mobile framework for supporting a plurality of bleacher seats thereon, and a plurality of pairs of leveling jacks located on opposite front and rear sides of the framework for stabilizing the framework on a ground surface when the framework is stationary. The invention includes a control station commonly located on each jack position on one side of the framework for allowing independent adjustment of each pair of jacks on the front and rear sides of the framework. The control station includes a pair of side-by-side, manual crank assemblies disposed upon an upper end of each jack positioned on one side of the framework. Each of the manual crank assemblies has a handle which is pivotable about a first horizontal axis extending generally parallel to the longitudinal axis of the framework, and is rotatable about a second horizontal axis extending generally perpendicularly to the first horizontal axis. The control station is preferably located on the rear side of the framework.
Various other objects, features and advantages of the invention will be made apparent from the following description taken together with the drawings.